[RFC 1/2] i2c: import multiplexed I2C bus core support from linux kernel
Antony Pavlov
antonynpavlov at gmail.com
Wed Nov 18 05:00:03 PST 2015
Signed-off-by: Antony Pavlov <antonynpavlov at gmail.com>
---
drivers/i2c/Kconfig | 7 +++
drivers/i2c/Makefile | 1 +
drivers/i2c/i2c-mux.c | 118 ++++++++++++++++++++++++++++++++++++++++++++++++++
include/i2c/i2c-mux.h | 40 +++++++++++++++++
include/i2c/i2c.h | 6 ++-
5 files changed, 171 insertions(+), 1 deletion(-)
diff --git a/drivers/i2c/Kconfig b/drivers/i2c/Kconfig
index 0c6aec3..21cf0ec 100644
--- a/drivers/i2c/Kconfig
+++ b/drivers/i2c/Kconfig
@@ -6,4 +6,11 @@ if I2C
source drivers/i2c/algos/Kconfig
source drivers/i2c/busses/Kconfig
+config I2C_MUX
+ tristate "I2C bus multiplexing support"
+ help
+ Say Y here if you want the I2C core to support the ability to
+ handle multiplexed I2C bus topologies, by presenting each
+ multiplexed segment as a I2C adapter.
+
endif
diff --git a/drivers/i2c/Makefile b/drivers/i2c/Makefile
index 648d844..5ce0d0a 100644
--- a/drivers/i2c/Makefile
+++ b/drivers/i2c/Makefile
@@ -1 +1,2 @@
obj-$(CONFIG_I2C) += i2c.o i2c-smbus.o busses/ algos/
+obj-$(CONFIG_I2C_MUX) += i2c-mux.o
diff --git a/drivers/i2c/i2c-mux.c b/drivers/i2c/i2c-mux.c
new file mode 100644
index 0000000..8c4952a
--- /dev/null
+++ b/drivers/i2c/i2c-mux.c
@@ -0,0 +1,118 @@
+#include <common.h>
+#include <malloc.h>
+#include <xfuncs.h>
+#include <of.h>
+#include <i2c/i2c.h>
+#include <i2c/i2c-mux.h>
+
+/* multiplexer per channel data */
+struct i2c_mux_priv {
+ struct i2c_adapter adap;
+
+ struct i2c_adapter *parent;
+ struct device_d *mux_dev;
+ void *mux_priv;
+ u32 chan_id;
+
+ int (*select)(struct i2c_adapter *, void *mux_priv, u32 chan_id);
+ int (*deselect)(struct i2c_adapter *, void *mux_priv, u32 chan_id);
+};
+
+static int i2c_mux_master_xfer(struct i2c_adapter *adap,
+ struct i2c_msg msgs[], int num)
+{
+ struct i2c_mux_priv *priv = adap->algo_data;
+ struct i2c_adapter *parent = priv->parent;
+ int ret;
+
+ /* Switch to the right mux port and perform the transfer. */
+
+ ret = priv->select(parent, priv->mux_priv, priv->chan_id);
+ if (ret >= 0)
+ ret = parent->master_xfer(parent, msgs, num);
+ if (priv->deselect)
+ priv->deselect(parent, priv->mux_priv, priv->chan_id);
+
+ return ret;
+}
+
+struct i2c_adapter *i2c_add_mux_adapter(struct i2c_adapter *parent,
+ struct device_d *mux_dev,
+ void *mux_priv, u32 force_nr, u32 chan_id,
+ int (*select) (struct i2c_adapter *,
+ void *, u32),
+ int (*deselect) (struct i2c_adapter *,
+ void *, u32))
+{
+ struct i2c_mux_priv *priv;
+ int ret;
+
+ priv = kzalloc(sizeof(struct i2c_mux_priv), GFP_KERNEL);
+ if (!priv)
+ return NULL;
+
+ /* Set up private adapter data */
+ priv->parent = parent;
+ priv->mux_dev = mux_dev;
+ priv->mux_priv = mux_priv;
+ priv->chan_id = chan_id;
+ priv->select = select;
+ priv->deselect = deselect;
+
+ /* Need to do algo dynamically because we don't know ahead
+ * of time what sort of physical adapter we'll be dealing with.
+ */
+ if (parent->master_xfer)
+ priv->adap.master_xfer = i2c_mux_master_xfer;
+
+ /* Now fill out new adapter structure */
+ priv->adap.algo_data = priv;
+ priv->adap.dev.parent = &parent->dev;
+ priv->adap.retries = parent->retries;
+
+ /*
+ * Try to populate the mux adapter's device_node, expands to
+ * nothing if !CONFIG_OF.
+ */
+ if (mux_dev->device_node) {
+ struct device_node *child;
+ u32 reg;
+
+ for_each_child_of_node(mux_dev->device_node, child) {
+ ret = of_property_read_u32(child, "reg", ®);
+ if (ret)
+ continue;
+ if (chan_id == reg) {
+ priv->adap.dev.device_node = child;
+ break;
+ }
+ }
+ }
+
+ /* FIXME */
+// priv->adap.nr = mux_dev->id;
+ priv->adap.nr = -1;
+ ret = i2c_add_numbered_adapter(&priv->adap);
+
+ if (ret < 0) {
+ dev_err(&parent->dev,
+ "failed to add mux-adapter (error=%d)\n",
+ ret);
+ kfree(priv);
+ return NULL;
+ }
+
+ dev_info(&parent->dev, "Added multiplexed i2c bus %d\n",
+ i2c_adapter_id(&priv->adap));
+
+ return &priv->adap;
+}
+EXPORT_SYMBOL_GPL(i2c_add_mux_adapter);
+
+void i2c_del_mux_adapter(struct i2c_adapter *adap)
+{
+ struct i2c_mux_priv *priv = adap->algo_data;
+
+ free(priv);
+}
+EXPORT_SYMBOL_GPL(i2c_del_mux_adapter);
diff --git a/include/i2c/i2c-mux.h b/include/i2c/i2c-mux.h
new file mode 100644
index 0000000..8022399
--- /dev/null
+++ b/include/i2c/i2c-mux.h
@@ -0,0 +1,40 @@
+/*
+ *
+ * i2c-mux.h - functions for the i2c-bus mux support
+ *
+ * Copyright (c) 2008-2009 Rodolfo Giometti <giometti at linux.it>
+ * Copyright (c) 2008-2009 Eurotech S.p.A. <info at eurotech.it>
+ * Michael Lawnick <michael.lawnick.ext at nsn.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#ifndef _LINUX_I2C_MUX_H
+#define _LINUX_I2C_MUX_H
+
+/*
+ * Called to create a i2c bus on a multiplexed bus segment.
+ * The mux_dev and chan_id parameters are passed to the select
+ * and deselect callback functions to perform hardware-specific
+ * mux control.
+ */
+struct i2c_adapter *i2c_add_mux_adapter(struct i2c_adapter *parent,
+ struct device_d *mux_dev,
+ void *mux_priv, u32 force_nr, u32 chan_id,
+ int (*select) (struct i2c_adapter *,
+ void *mux_dev, u32 chan_id),
+ int (*deselect) (struct i2c_adapter *,
+ void *mux_dev, u32 chan_id));
+
+void i2c_del_mux_adapter(struct i2c_adapter *adap);
+
+#endif /* _LINUX_I2C_MUX_H */
diff --git a/include/i2c/i2c.h b/include/i2c/i2c.h
index 3fab76d9..8f7aae9 100644
--- a/include/i2c/i2c.h
+++ b/include/i2c/i2c.h
@@ -245,7 +245,11 @@ extern struct list_head i2c_adapter_list;
extern struct i2c_client *
i2c_new_dummy(struct i2c_adapter *adap, u16 address);
-
+/* Return the adapter number for a specific adapter */
+static inline int i2c_adapter_id(struct i2c_adapter *adap)
+{
+ return adap->nr;
+}
extern int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num);
extern int i2c_master_send(struct i2c_client *client, const char *buf, int count);
--
2.6.2
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